The overall objective of this project is the in-depth investigation of the clinical features, natural history and immunologic mechanism(s) of hypersensitivity lung disease due to organic dust inhalation. Studies of piegeon breeders will be emphasized but as new organic dusts and affected individuals are identified they will also be entered into the project. It is likely that new agents and sensitized patients will be identified as more patients are suspected of having hypersensitivity lung diseases and our group has reportred several new antigens or sources of antigens over the past 15 years. Meeting the objectives will also be facilitated by studies of asymptomatic but similarly exposed individuals which will serve as comparison to those of patients with disease.